#include <bits/stdc++.h>
using namespace std;
const int N = 30;
int flag[N];

int main() {
	string s;
	getline(cin, s);
	for (int i = s.size() - 2; i > 0; i -= 3) {
		flag[s[i] - 'a']++;
	}
	int res = 0;
	for (int i = 0; i < 26; ++i) {
		if (flag[i] != 0) {
			res++;
		}
	}
	cout << res << endl;
	return 0;
}